Lung cancer is a type of cancer that begins in the lungs. In Singapore, it is the second most common cancer diagnosed each year. Smokers have the highest risk of developing of lung cancer. The risk of lung cancer increases with the duration and number of cigarettes smoked. Once one quits smoking, the chance of developing lung cancer decreases, although it takes years to equal that of a non-smoker. Passive smokers, eg non-smoking spouses of smokers also have an increased risk of developing lung cancer.
Types of lung cancer
There are two major types of lung cancer based on the appearance of cancer cells under the microscope. Treatment decisions are based on which type of lung cancer is present. The 2 major types of lung cancer are:
Small cell lung cancer. Small cell lung cancer occurs almost exclusively in heavy smokers and is less common than non-small cell lung cancer. Prognosis is poor as patients usually present late with disease that has spread.
Non-small cell lung cancer. This is the most common type of cancer. Non-small cell lung cancer is an umbrella term for several types of lung cancers that behave in a similar way. Non-small cell lung cancers include squamous cell carcinoma, adenocarcinoma and large cell carcinoma.
Symptoms of suspected lung cancer
Signs and symptoms of lung cancer typically may not be noticeable in the early stages. One should seek medical attention when any of the following signs or symptoms begin to be of concern to you:
- A cough that last more than 2 weeks
- Change in a chronic cough or “smoker’s cough”
- Coughing up blood (even if small amounts)
- Chest pain
- Unexplained weight loss
- Bone/joint pain
- Swelling of face or arms
- Facial paralysis
If you suspect you may have lung cancer, your doctor can order a number of tests to look for cancerous cells and to rule out other conditions. The first test is usually a chest X-ray. If the chest X-ray is abnormal, a chest CT Scan is usually ordered to clarify the abnormalities seen. Sometimes, CT picks up abnormalities that are not seen on a chest X-ray.
Subsequent tests may include:
Sputum cytology : If you have a cough and are producing sputum, looking at the sputum under the microscope can sometimes reveal the presence of lung cancer cells.
Lung biopsy : A sample of abnormal cells is removed in a procedure called a biopsy. Your doctor can perform a biopsy in a number of ways, including
Bronchoscopy : A lighted tube is inserted through the nose into the lungs. With it, your doctor is able to examine abnormal areas of your lungs and obtain lung tissue for analysis.
Mediastinoscopy : An incision is made at the neck and lymph node samples are taken.
Needle biopsy : Use of X-ray or chest CT to guide a needle through the chest wall and into the lung tissue to collect tissue samples.
Thoracocentesis / Pleural biopsy : This is to drain fluid out if the cancer has spread to the pleura (skin of the lungs)
A biopsy sample may also be taken from lymph nodes or other areas where cancer is thought to have spread, such as the liver.
Stages of Lung cancer
Once lung cancer is diagnosed, the doctor will order tests to determine the stage of your cancer. Staging determines the extent of the disease, specifically if the cancer has spread and where. To determine the stage of cancer, tests such as CT scans, magnetic resonance imaging (MRI), positron emission tomography (PET) and bone scans may be done to look for cancer spread beyond the lung.
Non small cell lung cancer is staged as 1 to 4. Stages 1 and 2 are early ie the cancer is limited to the chest. Stage 3 is also called locally advanced lung cancer and Stage 4 is late stage lung cancer, ie the cancer has spread to distant sites eg bones or brain.
Small cell lung cancer is usually staged as being limited or extensive. Limited stage indicates that cancer is limited to one lung. Extensive stage indicates that cancer has spread beyond the one lung.
Early stage lung cancer (Stage 1 and 2) can be cured by surgery. This usually involves removing a lobe of the lung (ie lobectomy) or the whole lung (pneumonectomy). Obviously, one has to be fit for surgery before it is contemplated. Lung function testing is mandatory before lung cancer surgery is attempted. Routinely, the surgeon samples the lymph nodes at operation to ensure that microscopic spread has not occured.
Late stage lung cancer (Stage 4) is usually treated with chemotherapy. One or a combination of chemotherapy drugs may be given intravenously or orally. This is done over a period of weeks or months, with breaks in between to allow the body to recover.
Over the past few years, new oral chemotherapy agents that work only in lung cancer patients with genotypic variants have been used. These oral drugs are called targeted therapy and are less toxic and easier to administer. However, they only work in those whose cancer tissues demonstrate genetic abnormalities eg EGFR and ALK mutants.
Radiation therapy uses high-powered energy beams, such as X-rays, to kill the cancer cells. Radiation therapy can be directed at the lung cancer from outside your body (external beam radiation) or it can be placed inside needles, seeds or catheters and inserted inside the body near the cancer (brachytherapy). Radiation therapy can be used alone or with other lung cancer treatments. Sometimes it’s administered at the same time as chemotherapy.
For very small tumours, stereotactic body radiotherapy may be used. This form of radiation aims many beams of radiation from different angles at the lung cancer. Stereotactic body radiotherapy treatment is typically completed in one or a few treatments. Radiotherapy is particularly used if the cancer has spread to the brain or bones.
The prognosis of lung cancer remains dismal , with 5-10% 5 year survival.